1. Field of the Invention
The present invention relates to a door lock system applicable to generally vehicles.
2. Description of the Related Art
As a door lock system to be applied to vehicles such as a four-wheeled vehicle, there is one including a link unit such as a torque cable that links a lock mechanism provided in the door and a key cylinder to each other. The lock mechanism is switched between an unlocked state that allows a door opening movement when an outside handle is operated to open the door, and a locked state that maintains the door being closed, even if the outside handle is operated to open the door, by making ineffective the door opening operation of the outside handle. The key cylinder is for key operations from the outside of the vehicle, and is provided on a door outer panel. In this key cylinder, a cylinder returning spring that keeps a normal position when a key operation is not performed is provided.
In this door lock system, when the key cylinder is rotated against an elastic force of the cylinder returning spring in response to a key operation, this rotating force is transmitted to a switching lever of the lock mechanism through the link unit to turn the switching lever from a neutral position to a switching position and switch the lock mechanism to an unlocked state or a locked state. When the key operation force is removed, the key cylinder is returned to the normal position by the cylinder returning spring and the switching lever is returned to the neutral position through the link unit.
A conventional door lock system has been disclosed, for example, in Japanese Published Unexamined Patent Application No. 2004-332449.
According to the conventional door lock system, the key cylinder can be provided on the door panel without depending on the position of the lock mechanism, thereby increasing degree of freedom of design and layout. However, sometimes, the relative positional relationship between the lock mechanism and the key cylinder influences the power transmission efficiency of the link unit. For example, when a torque cable is used as the link unit, although the key cylinder position with respect to the lock mechanism can be arbitrarily set by greatly bending the torque cable, lowering in power transmission efficiency is unavoidable.
In such a state with lowered power transmission efficiency, even when the cylinder returning spring returns the key cylinder to the normal position, the switching lever does not always return to the neutral position from the switching position. As a result, the lock mechanism may not be correctly switched by a successive key operation. This problem may occur not only when the torque cable is used but also when the key cylinder and the lock mechanism are linked via a link unit.